Oracle PL/SQL Programming, 5th Edition

Module Overloading

When more than one program in the same scope share the same name, the programs are said to be overloaded. PL/SQL supports the overloading of procedures and functions in the declaration section of a block (named or anonymous), package specifications and bodies, and object type definitions. Overloading is a very powerful feature, and you should exploit it fully to improve the usability of your software.

Here is a very simple example of three overloaded modules defined in the declaration section of an anonymous block (therefore, all are local modules):

DECLARE
   /* First version takes a DATE parameter. */
   FUNCTION value_ok (date_in IN DATE) RETURN BOOLEAN IS
   BEGIN
      RETURN date_in <= SYSDATE;
   END;

   /* Second version takes a NUMBER parameter. */
   FUNCTION value_ok (number_in IN NUMBER) RETURN BOOLEAN  IS
   BEGIN
      RETURN number_in > 0;
   END;

   /* Third version is a procedure! */
   PROCEDURE value_ok (number_in IN NUMBER) IS
   BEGIN
      IF number_in > 0 THEN
         DBMS_OUTPUT.PUT_LINE (number_in || 'is OK!');
      ELSE
         DBMS_OUTPUT.PUT_LINE (number_in || 'is not OK!');
      END IF;
   END;

BEGIN

When the PL/SQL runtime engine encounters the following statement:

IF value_ok (SYSDATE) THEN ...

the actual parameter list is compared with the formal parameter lists of the various overloaded modules, searching for a match. If one is found, PL/SQL executes the code in the body of the program with the matching header.

Note

Another name for overloading is static polymorphism. The term polymorphism refers to the ability of ...